This is a similar finding to that seen in MED caused by MATN3 mutations [Jackson et al., 2004; Makitie et al., 2004] and it is interesting to speculate that the genetic modifiers of phenotypic severity may be common across the spectrum of the pseudoachondroplasia-MED (PSACH-MED) bone dysplasia family, regardless of which gene the causative mutation resides in. This evidence concerns the gene COL9A1 and pseudoachondroplasia.